The present invention relates directly to the processing of metal powder and more particularly to a vertical chamber for degassing metal powders.
Metal powders occur some times as a by-product from a finishing process and at times they come into being intentionally as one of the intermediate steps in the formation of a finished metal product. In either event, there are various incentives for separating the metal powders from various contaminants or foreign materials which are mixed in with the metal powder. The primary separating techniques involve either heating the metal powder in a suitable reducing atmosphere, reacting the metal powder with an appropriate chemical reagent, or activating the powder by impact with energetic particles.
U.S. Pat. No. 3,954,458, Degassing Powder Metallurgical Products, teaches a powder metal degassing method. The powder in a compact which is considerably less than one hundred percent dense is subject to a very low absolute pressure and a temperature in the four hundred to eight hundred degree range for an amount of time which is dependent upon several factors including the size of the compact when the gas is removed. U.S. Pat. No. 2,329,862, Apparatus and Process for Treating Metal Powders, teaches the decarburization of iron powder containing chemically combined carbon. The powder is placed on a continuously moving horizontal support and passed through a hot zone. Variations on these concepts involving appropriate conditions of pressure and temperature are also known. Techniques for removing contaminants from fine metal powders which result from metal grinding operations are disclosed in U.S. Pat. No. 3,032,409, Metal Powder Purification. Organic contaminants such as oil, soap and detergents are removed by first dropping the contaminated powder through a current of hot gas and then mechanically advancing this powder through a second heating zone while agitating the powder in a horizontal drum. The application of magnetic fields electrostatic separation and air blowing techniques to additionally separate metal or carbon particles is also disclosed.
The chemical degassing of a powder is taught in U.S. Pat. No. 3,511,640, Degassing Platinum Powders. The specification teaches mixing finely divided platinum powder with a diluent metal oxide powder for a sufficiently long time at elevated temperature to separate the gases from the platinum powder. After the proper mixture has been maintained at temperature sufficiently, the material is cooled and the platinum powder separated from the metal oxide.
The third technique for removing impurities from metal powders is taught in such patents as U.S. Pat. No. 3,738,828, Method of Powder Activation and U.S. Pat. No. 4,005,956, Powder Activation and Integrated Powder Metallurgy System. The essence of these patents is to subject the powder to bombardment with high energy particles including electrons, ions or molecules in an appropriate inert or reducing atmosphere for removing the unwanted impurities from the powder.
Although such techniques for processing metal powder are known, industry is still in need of inexpensive equipment which is practical to operate and does a superior job of separating gas from metal powder.